In wireless communications systems, such as long term evolution (LTE) systems, downlink and uplink transmissions may be organized into two duplex modes: frequency division duplex (FDD) mode and time division duplex (TDD) mode. The FDD mode uses a paired spectrum where the frequency domain is used to separate the uplink (UL) and downlink (DL) transmissions. FIG. 1A is a graphical illustration of an uplink and downlink sub-frame separated in the frequency domain for the FDD mode. In TDD systems, an unpaired spectrum may be used where both UL and DL are transmitted over the same carrier frequency. The UL and DL are separated in the time domain. FIG. 1B is a graphical illustration of UL and DL sub-frames sharing a carrier frequency in the TDD mode. In LTE-Advanced, carrier aggregation allows expansion of effective bandwidth delivered to a user terminal through concurrent utilization of radio resources across multiple carriers. Multiple component carriers are aggregated to form a larger overall transmission bandwidth. Carrier aggregation may be performed in LTE-Advanced TDD or LTE-Advanced FDD systems.
The following terms and abbreviations may be used throughout this disclosure:
ACK Acknowledgement
A/N ACK/NACK
ARI ACK/NACK Resource Indicator
BPSK Binary Phase Shift Keying
CA Carrier Aggregation
CC Component Carrier
CCE Control Channel Element
CFI Control Format Indicator
CP Cyclic Prefix
CQI Channel-Quality Indicator
CRC Cyclic Redundancy Check
DAI Downlink Assignment Index
DCI Downlink Control Information
DL DownLink
DwPTS Downlink Pilot Time Slot
eNB Evolved Node B
E-UTRA Evolved Universal Terrestrial Radio Access
FDD Frequency Division Duplex
FEC Forward Error Correction
GP Guard Period
HARQ Hybrid Automatic Repeat reQuest
IDFT Inverse Discrete Fourier Transform
IE Information Element
LTE Long Term Evolution (aka E-UTRA)
MAC Medium Access Control
MIB Master Information Block
NACK Negative Acknowledgement
OCC Orthogonal Cover Code
OFDM Orthogonal Frequency Division Multiplexing
PBCH Physical Broadcast Channel
PCFICH Physical Control Format Indicator Channel
PHICH Physical Hybrid-ARQ Indicator Channel
PCell Primary Cell
PDCCH Physical Downlink Control Channel
PDSCH Physical Downlink Shared Channel
PMI Precoding-Matrix Indicator
PRACH Physical Random Access Channel
PUCCH Physical Uplink Control Channel
QPSK Quadrature Phase Shift Keying
RACH Random Access Channel
RF Radio Frequency
RS Reference Sequence
RI Rank Indicator
RNTI Radio Network Temporary Identifier
SCell Secondary Cell
SFN System Frame Number
SIB1 System Information Block Type1
SPS Semi-persistent Scheduling
SRS Sounding Reference Signal
TDD Time Division Duplex
TTI Transmission Time Interval
UCI Uplink Control Information
UE User Equipment
UL UpLink
UpPTS Uplink Pilot Time Slot